The present invention relates to a novel galectin. More specifically, isolated nucleic acid molecules are provided encoding human galectin 11. Galectin 11 polypeptides are also provided, as are vectors, host cells, recombinant methods for producing the same, and antibodies to galectin 11 polypeptides. The invention further relates to screening methods for identifying agonists and antagonists of galectin 11 activity. Also provided are diagnostic methods for detecting cell growth disorders and therapeutic methods for cell growth disorders, including autoimmune diseases, cancer, and inflammatory diseases.
Lectins are proteins that bind to specific carbohydrate structures and can thus recognize particular glycoconjugates. Barondes et al., J. Biol. Chem. 269(33):20807-20810 (1994). Galectins are members of a family of xcex2-galactoside-binding lectins with related amino acid sequences (For review see, Barondes et al., Cell 76:597-598 (1994); Barondes et al., J. Biol. Chem. 269(33):20807-20810 (1994)). Although a large number of glycoproteins containing xcex2-galactoside sugars are produced by the cell, only a few will bind to known galectins in vitro. Such apparent binding specificity suggests a highly specific functional role for the galectins.
Galectin 1 (conventionally termed LGALS1 for lectin, galactoside-binding, soluble xe2x88x921, but which is also known as: L-14-1, L-14, RL-14.5, galaptin, MGBP, GBP, BHL, CHA, HBP, HPL, HLBP 14, rIML-1) is a homodimer with a subunit molecular mass of 14,500 Daltons. Galectin 1 is expressed abundantly in smooth and skeletal muscle, and to a lesser extent in many other cell types (Couraud et al., J. Biol. Chem. 264:1310-1316 (1989). Galectin 1 is thought to specifically bind laminin, a highly polylactosaminated cellular glycoprotein, as well as the highly polylactosaminated lysosome-associated membrane proteins (LAMPs). Galectin 1 has also been shown to bind specifically to a lactosamine-containing glycolipid found on olfactory neurons and to integrin a7b1 on skeletal muscle cells.
Other members of the Galectin family have also been reported. Galectin 2 was originally found in hepatoma and is a homodimer with a subunit molecular mass of 14,650 Daltons (Gitt et al., J. Biol. Chem. 267.10601-10606 (1992)). Galectin 3 (a.k.a., Mac-2, EPB, CBP-35, CBP-30, and L-29) is abundant in activated macrophages and epithelial cells and is a monomer with an apparent molecular mass between 26,320 and 30,300 Daltons (Cherayil et al., Proc. Natl. Acad. Sci. USA 87: 7324-7326 (1990)). Galectin 3 has been observed to bind specifically to laminin, immunoglobulin E and its receptor, and bacterial lipopolysaccharides. Galectin 4 has a molecular mass of 36,300 Daltons and contains two carbohydrate-binding domains within a single polypeptide chain (Oda et al., J. Biol. Chem. 268:5929-5939 (1993)). Galectins 5 and 6 are discussed in Barondes et al., Cell 76:597-598 (1994). Human Galectin 7 has a molecular mass of 15,073 Daltons and is found mainly in stratified squamous epithelium (Madsen et al., J. Biol. Chem. 270 (11):5823-5829 (1995)).
Animal lectins, in general, often function in modulating cell-cell and cell-matrix interactions. Galectin 1 has been shown to either promote or inhibit cell adhesion depending upon the cell type in which it is present. Galectin 1 inhibits cell-matrix interactions in skeletal muscle presumably, by galectin 1-mediated disruption of laminin-integrin a7b1 interactions (Cooper et al., J. Cell Biol. 115:1437-1448 (1991)). In several non-skeletal muscle cell types, Galectin 1 promotes cell-matrix adhesion possibly by cross-linking cell surface and substrate glycoconjugates (Zhou et al., Arch. Bioch. Biophys. 300:6-17 (1993); Skrincosky et al., Cancer Res. 53:2667-2675 (1993)).
Galectin 1 also participates in regulating cell proliferation (Wells et al., Cell 64:91-97 (1991)) and some immune functions (Offner et al., J. Neuroimmunol. 28:177-184 (1990)). Galectin 1 induces the release of tumor necrosis factor from macrophages (Kajikawa et al., Life Sci. 39:1177-1181 (1986). Galectin 1 has also been demonstrated to have therapeutic activity against autoimmune diseases in animal models for experimental myasthenia gravis, and experimental autoimmune encephalomyelitis (Levi et al., Eur. J. Immunol. 13:500-507 (1983); and Offner et al., J. Neuroimmunol. 28:177-184 (1990), respectively). Additionally, galectin 1 has been shown to regulate immune response by mediating apoptosis of T cells (Perillo et al., Nature 378:736-739 (1995)).
Galectin 3 promotes the growth of cells cultured under restrictive culture conditions (Yang et al., Proc. Natl. Acad. Sci. USA 93:6737-6742 (June 1996)). Galectin 3 expression in cells confers resistance to apoptosis which indicates that galectin 3 could be a cell death suppresser which interferes in a common pathway of apoptosis. Id. Galectin 3 has also been observed to function in modulating cell-adhesion, as well as in the activation of certain immune cells by cross-linking IgE and IgE receptors.
Recently, a galectin-like antigen designated HOM-HD-21 was found to be highly expressed in a Hodgkin""s Disease cDNA library and another galectin, termed PCTA-1, was identified as a specific cell surface marker on human prostate cancer cell lines and patient-derived carcinomas.
Thus, galectins have been observed to be involved in the regulation of immune cell activity, as well as in such diverse processes as cell adhesion, proliferation, inflammation, autoimmunity, and metastasis of tumor cells. Accordingly, there is a need in the art for the identification of novel galectins which can serve as useful tools in the development of therapeutics and diagnostics for regulating immune response, inflammatory disease and cancer.
The present invention provides isolated nucleic acid molecules comprising, or alternatively consisting of, a polynucleotide encoding the galectin 11 polypeptide having the amino acid sequence shown in FIG. 1 (SEQ ID NO:2), the amino acid sequence encoded by the cDNA clone deposited in a bacterial host as ATCC Deposit No. 209053, on May 16, 1997, and fragments, variants, derivatives, and analogs thereof.
The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding the galectin 11 polypeptide having the amino acid sequence shown in FIG. 6 (SEQ ID NO:14), referred to herein sometimes as xe2x80x9cGalectin-11xcex1xe2x80x9d and fragments, variants, derivatives, and analogs thereof.
The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding the galectin 11 polypeptide having the amino acid sequence shown in FIGS. 6A-B (SEQ ID NO:14), referred to herein sometimes as xe2x80x9cGalectin-11xcex1xe2x80x9d and fragments, variants, derivatives, and analogs thereof.
The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding the galectin 11 polypeptide having the amino acid sequence shown in FIGS. 6A-B and 8 (SEQ ID NO:16), referred to herein sometimes as xe2x80x9cGalectin-11xcex2xe2x80x9d and fragments, variants, derivatives, and analogs thereof.
The galectin 11 of FIG. 1 (SEQ ID NOS:1 and 2), the galectin 11xcex1 of FIGS. 6A-B (SEQ ID NOS:24 and 25), and the galectin 11xcex2 of FIGS. 7-8 (SEQ ID NOS:26 and 27) are often referred to herein collectively as, e.g., xe2x80x9cGalectin-11xe2x80x9d.
The galectin 11 polynucleotide of FIG. 1 (SEQ ID NO:1), the galectin 11xcex1 polynucleotide of FIGS. 6A-B (SEQ ID NO:24), and the galectin 11xcex2 polynucleotide of FIG. 7 (SEQ ID NO:26) are often referred to herein collectively as, e.g., xe2x80x9cgalectin 11 polynucleotides.xe2x80x9d
The present invention also relates to recombinant vectors which include the isolated nucleic acid molecules of the invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of galectin 11 polypeptides by recombinant techniques.
The invention further provides isolated galectin 11 polypeptides, including galectin 11 of SEQ ID NO:2 and galectin 11xcex1 and xcex2, having an amino acid sequence encoded by a polynucleotide described herein and antibodies which bind these polypeptides. The galectin 11 polypeptide of FIG. 1 (SEQ ID NO:2), the galectin 11xcex1 polypeptide of FIGS. 6A-B (SEQ ID NO:25), and the galectin 11xcex2 polypeptide of FIG. 7 (SEQ ID NO:27) are often referred to herein collectively as, e.g., xe2x80x9cgalectin 11 polypeptides.xe2x80x9d
The present invention also provides screening methods for identifying compounds capable of enhancing or inhibiting a cellular response, such as, for example, apoptosis, induced by galectin 11. Generally, these methods involve contacting galectin 11, the candidate compound, and a cell which expresses a galectin 11 ligand, assaying a cellular response resulting from the binding of galectin 11 with the ligand, and comparing the cellular response to a standard, the standard being assayed when contact of galectin 11 and the galectin 11 ligand is made in the absence of the candidate compound; whereby, an increased cellular response over the standard indicates that the compound is an agonist and a decreased cellular response over the standard indicates that the compound is an antagonist.
In another aspect, a screening assay for agonists and antagonists is provided which involves determining the effect a candidate compound has on galectin 11 binding to a xcex2-galactoside sugar. In particular, the method involves contacting a xcex2-galactoside sugar with a galectin 11 polypeptide and a candidate compound and determining whether galectin 11 binding to the xcex2-galactoside sugar is increased or decreased due to the presence of the candidate compound.
The invention also provides diagnostic methods useful during diagnosis of disorders associated with elevated, decreased, or otherwise aberrant expression of galectin 11.
The invention further provides for methods for treating an individual in need of an increased level of galectin 11 activity in the body comprising, administering to such an individual a composition comprising a therapeutically effective amount of an isolated galectin 11 polypeptide, fragment, variant, derivative, or analog of the invention, or an agonist thereof.
In another embodiment, the invention provides for methods for treating an individual in need of a decreased level of galectin 11 activity in the body comprising, administering to such an individual a composition comprising a therapeutically effective amount of a galectin 11 fragment, variant, derivative, analog or antibody of the invention or galectin 11 antagonist.